The readily accessible display of news and information, particularly in view of the rapidly changing and increasing speed of modern telecommunications, is becoming increasingly critical for use in commercial enterprises, leisure businesses and to the community at large. Display's of the type typically known in the industry are currently advantageously provided by electronic display signs, e.g. the “Traveling Word” screen display devices applying conventional LED matrix architecture, for instance LED's arranged in rows and columns in a matrix configuration, for use in stock exchanges or for public messaging and advertisements were invented, developed and installed in the early 1980s. These screens provided ready access to fiscal information that, by its very nature is constantly and rapidly changing.
The use of LEDs as light sources in patterns of rows and columns for displaying information is well known. Various features are comprehensively described in U.S. Pat. No. 5,796,362 issued to Banks. In that patent are disclosed large modular, electronic display sources comprising a sign controller, sign systems buses for data transmission, display panels, and panel control cards associated with each panel. This display sign supports for example 512 LEDs.
A static display unit is also disclosed in international patent application WO 90/12354 to Stella Communications Limited which is described as mounted on a motor driven, rotary unit. The unit provides cylindrical display from LEDs arranged in vertical columns which sweep around a cylindrical surface. The rotating unit carries a unit for controlling the LEDs and a memory.
Both international application filed by Lumino Licht Electronik GmbH, (“Lumino”) numbers WO 97/50070 published on Dec. 31, 1997 and WO 98/33164 published on Jul. 30, 1998, relate to rotational display devices within a housing. WO 97/50070 describes a device for displaying alphanumeric characters and/or symbols, within a rotationally symmetric housing (19) of a transparent and/or translucent material; the housing (19) contains an electric motor (2) with a motor shaft (20) which revolves around a symmetrical axis (21); a carrier (5) which is rotationally fixed to the motor shaft (20) and on which is attached at least one row of light-emitting diodes or groups of light-emitting diodes (6) that are substantially perpendicular to the motor shaft (20); and a circuit board (4) with a control circuit for the light-emitting diodes (6). To improve control of the display device and the LED's and to provide for a technically simple series production, the display device also has an opto-electronic measuring device (15) made of a transmitter (22) and receiver (23), to measure the rotating speed of the carrier (5) for synchronizing control of the light-emitting diodes (6) with the rotating speed of the carrier (5), the transmitter and receiver are fixed to a rotating structural part of the device on the one hand and to a stationary structural part of the device on the other hand, at a short distance apart. With the use of software the signal picked up by the receiver can be converted into a clear square-wave signal, free from external interference so that the LED-control can be synchronized with the exactly or almost exactly measured rotating speed of the carrier (5). The device according to the invention also contains a mechanical balancing element (6, 8) opposite the carrier (5) in relation to the symmetrical axis (21), wherein the balancing element (7, 8) is a rod (7) of any cross-section, the operating length of which can be shortened, the rod being raised into a substantially horizontal position during operating.
WO 98/33164 relate to a spherical display device with a circuit board (4), accommodated inside a spherical housing (31), with drive and control elements and electronic components, as well as a support (5) rotating inside the housing (31) for light-emitting diodes or light-emitting diode groups (6). Transmission of electric energy onto the circuit board (4) is conducted by contactless inductive energy transmission. It is a critical feature of both WO 97/50070 and WO 98/33164 that contactless inductive transmission of electrical energy and/or data is provided to the circuit board and its circuits. It is also a critical feature to interface the device with programming means to control to the LEDs synchronously with the rotating speed of the carrier which, preferably, is rotated by a synchronous motor.
A disadvantage of the prior art proposals is the use of an induction motor having windings on its rotor connected to a power supply by slip rings or brushes which are disconnected to reduce wear with the slip rings being short circuited so that the rotor functions essentially as a squirrel cage motor (a slip ring induction motor). This type of motor is susceptible to wear and production of electrical noise potentially interfering with data controlling the LED display.